Research on Hydrodynamic and Water Quality Optimization Scheduling Based on Optimization Technology for Complex of River Network Structures

Many problems occur in plain river networks, such as low river flow and severe water environment pollution. Water diversion is important for water environment improvement in plain river network areas. Adopting Sanshanwei in Foshan city as an example, a river network hydrodynamic and water quality coupling model was constructed based on structural optimization technology for complex gate-controlled tidal river networks. Fifteen-day continuous hydrodynamic water quality monitoring data were used for model validation. Two model performance evaluation indices, NSE and RMSE, were employed for model reliability evaluation. Considering terrain, tidal pattern and landscape water level, five optimal scheduling conditions (C1-C5) were designed. The hydrodynamic water quality improvement effect was simulated under different working conditions, and the comprehensive influence mechanisms of tide level, drainage flow and spatial distribution, water quality and river water level were examined. Water pollution was evaluated by a single-factor pollution index. The results indicated a reasonable and reliable model. The river network structure optimization method is universal. Under C1 to C5, the average pollutant reduction rates in the monitoring section were 28.69%, 34.05%, 0.77%, -44.49% and -144.69%. The river network water environment was improved under C1, C2 and C3, from Moderate pollution to Light, Mminor and Light pollution respectively. A river section with high water quality requirements should be used as the upstream section of the water replenishment path. Comprehensively considering the effects of river flow distribution, flow path, branch river diversion and outer river pollutant concentration on river water quality, and combining the dynamic water environment capacity of the tidal river network and spatial and temporal distributions of pollution source discharge, the water environment improvement effect was high significant. These results provide important technical support for water environment management in gate-controlled plain river network areas eliminate black and odorous urban water bodies.